The synthesis, turnover, and function of intestinal brush border proteins will continue to be studied. The specific proteins currently under investigation are alkaline phosphatase in suckling rats, intrinsic factor (IF) receptor in dog ileum, and apolipoproteins in rat and human jejunum. We will study the incorporation of alkaline phosphatase from somewhere in the cell cytosol into the membrane. The process whereby this happens will be investigated. The intrinsic factor receptor will be purified to determine its structure and relationship to lipids, and to ascertain how IF and B12 are dissociated from the complex. Finally, apolipoprotein synthesis will be studied to contrast it to alkaline phosphatase, one protein made for export from the cell, one for insertion into the membrane.